As the whole world has been discussing global warming as a serious problem, the importance of developing a refrigeration unit that has a low environmental load has increased. Refrigerants themselves have an impact on global warming and also greatly affect the performance of refrigeration units. Accordingly, the selection of a refrigerant plays an important role in reducing the generation of carbon dioxide, which is involved in global warming.
In recent years, various types of fluorinated propenes having a double bond in the molecule have been proposed. These fluorinated propenes have a lower global warming potential (GWP) compared to heretofore known chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs).
One of them is 2,3,3,3-tetrafluoropropene (HFO1234yf) (Patent Literatures 1, 2, etc.). However, HFO1234yf has a drawback: the device performance cannot be ensured when HFO1234yf is used alone in conventional devices because HFO1234yf has a higher boiling point and a lower pressure compared to HCFC22, which has conventionally been used in floor standing type air conditioners, and non-ozone layer depleting R407C and R410A, which have subsequently been promoted as alternatives.
When selecting a refrigerant, while it is obviously important that the refrigerant itself has a low GWP (a direct impact on global warming), the energy use efficiency (an indirect impact on global warming) of a device that uses the refrigerant is equally or more important. In recent years, the annual performance factor (APF) has been used as a method for evaluating the energy efficiency of devices.
The APF is a numerical value determined by dividing the cooling and heating capacity required in one year if an air conditioner is used throughout the year by the amount of electricity consumed by the air conditioner in one year (the amount of electricity consumption over a specific period of time). The evaluation closely reflects actual use. An air conditioner having a higher APF achieves higher energy-saving performance, and a refrigerant thereof is considered to have a lower environmental load.